1. Field of the Art
This invention relates to a method and an apparatus for treating surfaces of substrate plates such as of liquid crystal display panels, semiconductor wafers, magnetic disks, optical disks and so forth, and more particularly to a method and an apparatus for washing or etching surfaces of substrate plates of glass, semiconductor, synthetic resin, ceramics, metal or composite material of these substances under irradiation of ultraviolet ray.
2. Prior Art
For instance, in the case of a TFT substrate which constitutes a transparent substrate of a liquid crystal display panel, circuit patterns including transparent electrodes are formed on its surface by the use of film forming means. In the course of an LCD panel fabrication process, surfaces of LCD panel substrate plates are processed through washing and etching treatments. In treating substrate plates of this sort, it has been the general practice to resort to the so-called wet process in which a treating liquid is applied or sprayed on the surface of each substrate plate. However, recently a dry process by irradiation of ultraviolet ray is increasingly employed for the washing and etching treatments of various substrate plates.
In this regard, disclosed in Japanese Laid-Open Patent Application 2001-137800 is a process for treating substrate plates under irradiation of ultraviolet ray. In this prior art process, while being transferred on a conveyer means, substrate plates to be treated are passed through a lower portion of a lamp house which is internally provided with a dielectric barrier discharge lamp and supplied with a moistened inert gas, i.e., a mixture of water vapor and an inert gas. The energy of irradiated ultraviolet ray from the dielectric barrier discharge lamp act on organic contaminants which have deposited on the surface of a substrate plate, breaking up chemical bonds in organic contaminants and decomposing same into substances of low molecular weight. In addition, the ultraviolet ray also act on water vapor in the atmosphere and decompose water to produce a reducing active member [H.] and an oxidative active member [.OH]. As a consequence, the low molecular weight substances which exist on the substrate surface are converted into volatile substances through reduction or oxidation, by reactions with the reductive and oxidative members [H.] and [.OH], and released from the substrate surface. Thus, the substrate surface is cleaned and at the same time improved in wettability.
In this connection, if oxygen exists in the atmosphere in which a substrate plate is irradiated with ultraviolet ray from a dielectric barrier discharge lamp, the energy of ultraviolet light ray is absorbed and attenuated by oxygen. As a result, the capacity of decomposing organic contaminants on the substrate surface is impaired to a considerable degree. Therefore, it is extremely important to control the atmosphere of ultraviolet irradiation, more specifically, to provide a dielectric barrier discharge lamp within a treating chamber which is arranged to exclude oxygen from the atmosphere within the chamber as much as possible. A mixture gas consisting of water vapor and an inert gas and is supplied to the treating chamber as mentioned above, for the purpose of generating the necessary active members [H.] and [.OH] on and in the vicinity of a substrate plate in a concentrated manner. Further, the internal pressure of the treating chamber needs to be maintained at an elevated level in order to shield from air entrance and exit openings which are provided at the upstream and downstream ends of the treating chamber.
Thus, it is an utmost importance to maintain, within a treating chamber, a moistened inert gas atmosphere which is free of oxygen, in order to effectively generate the above-mentioned active members, which contribute the decomposition of organic contaminants on the surfaces of a substrate plate under irradiation of ultraviolet ray from a dielectric barrier discharge lamp, and to carry out a washing or other treatment to an extremely high accuracy. In this regard, the above-mentioned prior art has a problem as explained below.
Namely, as a substrate plate is transferred into a treating chamber from outside, air is inevitably admitted into the treating chamber along with the substrate plate. Especially, due to its viscosity, an air layer which exists on the surface of the substrate plate remains stuck on the substrate surface even after admission into the treating chamber. Therefore, if the substrate plate in this state is advanced to an irradiating position under a dielectric barrier discharge lamp in the treating chamber, considerable energy losses are caused by the air layer which absorbs the energy of ultraviolet ray, even in a case where the atmosphere in the treating chamber is strictly controlled.
With the foregoing situations in view, it is an object of the present invention to provide a method and an apparatus for treating a surface of a substrate plate under irradiation of ultraviolet ray emitted from a dielectric barrier discharge lamp, suppressing energy loss of ultraviolet ray to a minimum by removing oxygen from or in the vicinity of a treating surface of the substrate plate prior to irradiation of ultraviolet ray from the dielectric barrier discharge lamp.
According to the present invention, the above-stated objective is achieved by the provision of a method for treating a surface of a substrate plate under irradiation of ultraviolet ray emitted from a dielectric barrier discharge lamp, which comprises the steps of: removing oxygen on and in the vicinity of a treating surface of the substrate plate; supplying humidified inert gas toward the substrate plate to humidify the treating surface and surrounding atmosphere of the substrate plate; and irradiating the treating surface of the substrate plate with ultraviolet ray from the dielectric barrier discharge lamp.
According to a preferred form of the present invention, there is provided a method for treating a surface of a substrate plate while being transferred horizontally across a treating chamber under irradiation of ultraviolet ray emitted from a dielectric barrier discharge lamp, which comprises the steps of: removing oxygen or air on and in the vicinity of a treating surface of the substrate plate by blasting a sweeping inert gas thereto from a direction opposite to substrate transfer direction; supplying a water vapor-containing humidified inert gas obliquely toward the substrate plate in a forward direction in the substrate transfer direction to humidify the treating surface and surrounding atmosphere of the substrate plate; and irradiating the treating surface of the substrate plate with ultraviolet ray from the dielectric barrier discharge lamp thereby cracking water vapor into a reductive active member [H.] and an oxidative active member [.OH] for reaction with contaminant substances on the treating surface.
According to the present invention, there is also provided an apparatus for treating a surface of a substrate plate under irradiation of ultraviolet ray, comprising: a treating chamber provided in part of a path along which a substrate plate is transferred horizontally by a conveyer means, the treating chamber being provided with a dielectric barrier discharge lamp for irradiating ultraviolet ray on a treating surface of the substrate plate; a humidified inert gas feed means located at a position upstream of an irradiating region of the dielectric barrier discharge lamp in substrate transfer direction thereby to supply a humidified inert gas toward the treating surface of the substrate plate; and an oxygen removing means located at a position upstream of the humidified inert gas feed means in the substrate transfer direction for removing oxygen from the treating surface and surrounding atmosphere of the substrate plate.
The above and other objects, features and advantages of the present invention will become apparent from the following particular description of the invention, taken in conjunction with the accompanying drawings which show by way of example some preferred embodiments of the invention. Needless to say, the present invention is not limited to particular forms shown in the drawings.